Overheating under load

[Galvez83]

Guys i have a question regarding a broken seal on the TSK SX-M water intake tube. I kept overheating under load and decided to go ahead and replace manifolds and risers due to age. After replacement still overheating under load. I checked impeller which was new and still in good shape. Circ pump is new, hoses from oil cooler to raw water pump is new. I took off the drive DP-SM and found crushed and broken seal around the water intake tube. I gues when the drive was installed it crushed it. Either way i still ordered the pick up tube, o ring, hose and gasket to replace. But i wondered if it could be a possibility of causing the overheat under load. The outdrive pick up tube grommet had been changed a couple of months ago.

 

[kenny nunez]

Add a piece of clear hose just where the supply hose enters the thermostat housing. This will show if there is an air leak on the incoming supply.
Have someone watch the clear hose before and when on plane. If there are bubbles after the boat planes then the drive is the problem. If the water completely disappears when the boat is planing then you have a head gasket problem because the combustion pressure overcomes the water pump’s pressure.

 

[HiWard]

Are you referring to the seal for the cooling water intake between the pivot housing and upper gear housing? If this seal is broken, the pump will suck air when the boat is on plane. That could be the cause of your overheat issue.

 

[Galvez83]

Are you referring to the seal for the cooling water intake between the pivot housing and upper gear housing? If this seal is broken, the pump will suck air when the boat is on plane. That could be the cause of your overheat issue.

Yes that is correct. Number 28 on the drawing. I found it crushed and broken. I still replaced it but had that concern regarding overheating under load. I also went ahead and replaced 25, 23, 24 and 27 on diagram.

 

[cptbill]

When the drive is down that tube and seal may or may be submerged so as was said it important to find out if it's sucking air. Over heating under load could also be caused by a restriction in the in the water passages, like a piece of impeller stuck somewhere or another cooling passage clogged

 

[Galvez83]

When the drive is down that tube and seal may or may be submerged so as was said it important to find out if it's sucking air. Over heating under load could also be caused by a restriction in the in the water passages, like a piece of impeller stuck somewhere or another cooling passage clogged

Correct i had a fin from an old impeller that i replaced that i am still looking for it. I took apart the water pump impeller and hose and no success.

 

[Lou C]

Remove the thermostat housing and take out the stat, it is likely to be in there.

 

[kenny nunez]

It might be lodged in the thermostat housing.

 

[Galvez83]

Found a piece inside circ pump. Checked inside stat housing and nothing there. Also checked hoses to manifolds and nothing there. Port riser and manifold seem to heat up more that the starboard even though both risers and manifolds are new. This is a reman motor running perfect other than the overheating under load.

 

[kenny nunez]

It is normal for the manifolds to have a different temperature. Sometime it can be balanced by trying different size stainless flat washers to the manifold inlet of the cooler manifold. A infrared temperature gun would help.

 

[muc]

Did you run a stiff wire through the bypass passage that is in the pic Lou C posted? That passage getting plugged is a common problem. Metal coat hanger works good.

 

[Galvez83]

Update.....changed a couple of things but have not taken the boat to the water yet due to a large oil leak between timing cover and oil pan recently discovered. I did test it with muffs and so far so good, temp stays at 160. I did notice that the temp climbed if i raised the rpms but slowly settled down once at idle (on muffs). Items changed are the gasket at the outdrive, plastic fitting with nut and hose at bell housing going to transom. I was told by a local mechanic that since i boat in sunny Miami, Florida that i should run a 140 thermostat. Is there any truth behind that? My thermo is 160 brand new and kitchen tested with IR thermometer. If that is the case will drilling a hole help it or just flat out replace it with a 140? The oil leak has me at bay until engine comes out for oil pan gasket replacement but i can still deal with the thermostat issue.

 

[Horigan]

If you saw the temp climb on muffs, with no real load, then I suspect you still have an issue.

I believe 140F thermostats are more for raw water cooled systems, whereas 160F is used for closed systems with a heat exchanger.

 

[Galvez83]

If you saw the temp climb on muffs, with no real load, then I suspect you still have an issue.

I believe 140F thermostats are more for raw water cooled systems, whereas 160F is used for closed systems with a heat exchanger.

I dont have closed cooling. Outdrive draws from the sea (raw). I will then order a 140 and recheck. Will still investigate further into the heating up issue and provide update.

 

[Bondo]

Update.....changed a couple of things but have not taken the boat to the water yet due to a large oil leak between timing cover and oil pan recently discovered. I did test it with muffs and so far so good, temp stays at 160. I did notice that the temp climbed if i raised the rpms but slowly settled down once at idle (on muffs). Items changed are the gasket at the outdrive, plastic fitting with nut and hose at bell housing going to transom. I was told by a local mechanic that since i boat in sunny Miami, Florida that i should run a 140 thermostat. Is there any truth behind that? My thermo is 160 brand new and kitchen tested with IR thermometer. If that is the case will drilling a hole help it or just flat out replace it with a 140? The oil leak has me at bay until engine comes out for oil pan gasket replacement but i can still deal with the thermostat issue.

Ayuh,..... Yer motor needs to come out, as the oil pan needs to come off, to fix the timing cover,.....

 

[Lou C]

Yep as Bondo says, you got some more work to do, first.
As far as the 140 stat vs the 160 stat, to the best of my knowledge, V/P specified a 160 (even in salt water) for the majority of their engines. Because I heard this so many times (gotta have a 140 in salt not a 160) I looked into it myself. My use is 100% salt, not Florida or Gulf coast salt but salt, none the less.
What I found:
the supposed clogging of cooling passages with calcium deposits doesn't happen in all cases if you use a 160 stat, how do I know that? Well I took apart my engine in 2017 to replace blown head gaskets, and didn't really see that anywhere, a little deposits here and there but most was plain old cast iron rust.
Also, the only VP engine that I know of that used a 140 stat, was some of the big block 7.4 liters. So I got one of those stats, and tried it. The engine took longer to warm up and ran too cold, except when it was up on plane. I wound up going back to the 160 stat I used for all those years. Not saying it is right in all salt water environments but for me, it wasn't really beneficial. Running too cold, isn't good either. In fact that's one of the main benefits or closed cooling, the engine runs at the temp it was designed to run at. In fact the cold running of outboards, creates problems for them too, fuel dilution of the motor oil being one of them.

 

[Lou C]

Here's the old cyl heads, the water passages are the ones at the extreme end of the heads. Bit of calcium there, but not clogged.

 

[cptbill]

While you have the engine out don't forget to check things like the PS fluid cooler and the return fuel cooler if you have one

 

[Lou C]

and definitely the steering actuator and steering cable, exhaust Y pipe, starter motor, bilge pump etc.

 

[Galvez83]

Well now we have either piston slap or rod knock in the mix. Working with the mechanic to determine a noise under load. Imagine that, a brand new engine with less than 5 hours.